The present invention relates to a power consumption control system for effectively saving power consumption in an electronic device which is controlled in synchronism with a clock pulse from an oscillator circuit and digitally processes data.
The electronic device of this type is miniaturized and mostly uses a battery as a power source. Therefore, the important problem in this type of device is how to reduce the power consumption of the electronic device. One of the proposals is to prevent the useless power consumption of the battery when an operator fails to turn off the power switch of the electronic device. More specifically, a so-called automatic turn off system is known in which, after a given time lapses from the final key operation, a power source to drive the respective circuits is automatically turned off. This method is effective to save wasteful power consumption. However, when the key operation is held an in interrupted state during the operation for some reason, the power source is shut off upon a lapse of a given time after any key has been depressed immediately before it is put into the interrupted state. As a result, the results of the operations are all cleared. In such a case, the operation must be newly performed again. This is very onerous for the operator.
The consumed power of CMOS (complementary type MOS) LSI chips, which has been employed in the electronic circuit of an electronic calculator in recent days, is generally expressed by fCV.sup.2 where f is the frequency of the signal to the drive circuits, C is a stray capacitance and V is the operating voltage. It can be seen from the expression that the decrease of the effective frequency f reduces the power consumption of the calculator.
The conventional electronic calculator with an automatic power off function involves another technical problem in releasing the automatic power off state. To release the automatic power off state, the conventional calculator uses a special key provided for the purpose of that release. Another conventional device employs an ON key and an OFF key and the ON key is used for releasing the automatic power off mode. A further conventional calculator uses one (for example, a C (clear) key) of the various keys arranged in the key input section to release the automatic power off mode. The former cases need additional keys for its purpose. This leads to an increase of the number of keys and hinders the miniaturization of the device. The latter case does not need an additional key but an operator must search for the specified key for the release from a number of keys. Further, before the data entering or the data processing of an input, an operator must depress a key utterly unrelated to such operations. Therefore, the operability of the calculator is considerably deteriorated.
Accordingly, an object of the invention is to provide a power consumption control system for effectively saving power consumption in an electronic device which is controlled in syncrhonism with a clock pulse from an oscillator circuit and digitally processes data.
Another object of the invention is to provide a power consumption control system for effectively saving power consumption in electronic digital data processing devices, which can considerably reduce the power consumption without interrupting the power source. To achieve this object, after a given time lapses from the final key-in operation in a power on state, an oscillating circuit to produce a clock pulse for forming various timing signals necessary for the circuit operation is automatically stopped thereby to decrease the effective frequency f.
Another object of the invention is to provide a power consumption control system for effectively saving power consumption in the electronic device which can effectively release the automatic power off mode when the operation of a key is performed after the automatic power off mode is set up.
Another object of the invention is to provide a power consumption control system which can release the automatic power off mode by the operation by a proper key and at the same time can judge if the data processing for the depressed key is performed or not.
In the specification, the term "automatic power off" means that a power source system of the electronic device is automatically stopped and that the electronic device is placed in a low power consuming state substantially equivalent to a state that the power source is shut off.
In the power consumption control system according to the invention, a pulse generator which consumes a relatively large power in the electronic device is stopped, so that the drive of the electronic device is stopped as if the power source is shut off.
Accordingly, the term "automatic power off" in the specification of the present application is slightly different from the sensed usually used. Since it has the same meaning as the general "automatic power off", however, the same term is used.